Channel state information request/feedback method and apparatus

ABSTRACT

A Channel State Information (CSI) request/feedback method and apparatus for a wireless communication system supporting carrier aggregation or bandwidth extension are provided. A base station sets a CSI request field of an Uplink (UL) grant for scheduling UL transmission on a UL Component Carrier (CC) corresponding to a Downlink (DL) CC of which CSI is requested, to a request value. The UL grant is transmitted to a terminal.

PRIORITY

This application claims priority under 35 U.S.C. §119(a) to anapplications filed in the Korean Intellectual Property Office on Apr. 8,2010 and Jun. 18, 2010, and assigned Serial Nos. 10-2010-0032200 and10-2010-0058154, respectively, the contents of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to wireless communications, andmore particularly, to a channel state information request/feedbackmethod and apparatus for a wireless communication system supportingcarrier aggregation or bandwidth extension.

2. Description of the Related Art

Long Term Evolution-Advanced (LTE-A) is standardized by the 3^(rd)Generation Partnership Project (3GPP). In the 3GPP, a BandwidthExtension technique is discussed to support a peak data rate that iscomparatively higher than the LTE Release 8.

The Bandwidth Extension, based on the Carrier Aggregation technique, canextend the bandwidth beyond a single LTE Release 8 system bandwidth. Inthe Bandwidth Extension, each bandwidth for transmission is called aComponent Carrier (CC).

A Release 8 LTE User Equipment (UE) is specified to use a singleComponent Carrier in UpLink (UL) and DownLink (DL), respectively.

The Component Carriers (CCs) can be aggregated contiguously ornon-contiguously in a frequency domain.

FIG. 1 is a diagram illustrating a relationship of a DL CC 100 and a ULCC 101 in the LTE Release 8 system.

In LTE Release 8, each UE performs communication with the single DL CC100 and the single UL CC 101. The UL grant and DL assignment aretransmitted on the DL CC 100, and the PUSCH corresponding to the ULgrant is transmitted on the UL CC 101 associated with the DL CC 100. InFIG. 1, the solid line connecting the DL CC 100 and the UL CC 101 showsthe relationship between the DL CC 100 and the UL CC 101 on which thePUSCH transmission is scheduled by means of the UL grant transmitted onthe DL CC 100.

When data to be transmitted occurs, the LTE Release 8 UE receivesscheduling information for transmitting a Physical Uplink Shared Channel(PUSCH) in a Physical Downlink Control Channel (PDCCH) transmitted by abase station (eNodeB or eNB). The scheduling information can be calledan UL grant. In LTE Release 8, only one Downlink Control Information(DCI) format, i.e. DCI format 0, is defined for the UL grant. In orderto check the channel state of the downlink carrier on which the PDCCH istransmitted, the eNB requests the UE for aperiodic Channel StateInformation (CSI) with a 1-bit CSI request field of DCI format 0. Whenthe signal of DCI format 0 is received, the UE analyzes the CSI requestfield contained in the received signal, measures channel state in thesubframe in which the signal is received, and feeds back the measuredaperiodic CSI of the DL CC 100 to the eNB. The aperiodic CSI ismultiplexed with the data to be transmitted by the UE on the PUSCH.Although the aperiodic CSI is multiplexed with the data to betransmitted by the UE on the PUSCH, it is simply referred to as“transmits aperiodic CSI” herein.

In LTE-A, a UE can communicate multiple downlink Carrier Componentsand/or multiple uplink Carrier Components with the bandwidth extensiontechnique. When using carrier aggregation, however, the conventionalmethod has is problematic when the eNB requests the aperiodic CSI andthe UE feeds back the requested aperiodic CSI.

SUMMARY OF THE INVENTION

The present invention has been made to address at least the aboveproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the present inventionprovides a channel state information request/feedback method andapparatus for a wireless communication supporting bandwidth extensiontechnique that enables an eNB requests for aperiodic channel stateinformation of a downlink component carrier and enables a UE to measureand feed back the channel state of the downlink component carrier.

According to one aspect of the present invention, a CSI request methodof a base station is provided. A CSI request field of a UL grant forscheduling UL transmission on a UL CC corresponding to a DL CC of whichCSI is requested, is set to a request value. The UL grant is transmittedto a terminal.

According to another aspect of the present invention, a base station isprovided for requesting a terminal for a CSI. The base station includesa scheduler that sets a CSI request field of a UL grant for schedulingtransmission on a UL CC corresponding to a DL CC of which CSI isrequested, to a request value. The base station also includes atransmitter that transmits the UL grant to the terminal.

According to an additional aspect of the present invention, a CSIfeedback method of a terminal is provided. A UL grant is received from abase station. A CSI request field of the UL grant is analyzed. When theCSI request field is set to a request value, a CSI of a DL CCcorresponding to an UL CC scheduled by means of the UL grant isgenerated by measuring channel state of the UL CC. The CSI is fed backto the base station on the UL CC scheduled by means of the UL grant.

According to a further aspect of the present invention, a terminal isprovided for feeding back a CSI to a base station. The terminal includesa receiver that receives a UL grant from the base station. The terminalalso includes a PDCCH decoder that decodes a CSI request field of the ULgrant. The terminal further includes an aperiodic CSI encoder whichmeasures, when the CSI request field is set to a request value, channelstate of a DL CC corresponding to the UL CC scheduled by means of the ULgrant and generates a CSI with the measured channel state. The terminaladditionally includes a transmitter that transmits the CSI to the basestation on the UL CC scheduled by means of the UL grant.

According to another aspect of the present invention, a CSI requestmethod of a terminal is provided. A UL grant is configured having a CSIrequest field set to a request value and an identifier of a DL CC ofwhich CSI is requested. The identifier is set according to a ruleconfigured by a higher layer. The uplink grant is transmitted to theterminal.

Additionally, according to another aspect of the present invention, abase station is provided for requesting a terminal for CSI. The basestation includes a scheduler that configures a UL grant having a CSIrequest field set to a request value and an identifier of a DL CC ofwhich CSI is requested. The identifier is set according to a ruleconfigured by a higher layer. The base station also includes atransmitter that transmits the UL grant to the terminal.

Further, according to another aspect of the present invention, a CSIfeedback method of a terminal is provided. A UL grant is received from abase station. A CSI request field of the UL grant is analyzed. When theCSI request field is set to a request value, a DL CC is selectedaccording to a rule configured by a higher layer and DL CCidentification information included in the UL grant. A CSI is generatedby measuring channel state of the selected DL CC. The CSI is transmittedto the base station on the UL CC scheduled by means of the UL grant.

According to another aspect of the present invention, a terminal isprovided for feeding back CSI to a base station. The terminal includes areceiver that receives a UL grant from the base station. The terminalalso includes a PDCCH decoder that decodes a CSI request field of the ULgrant. The terminal further includes an aperiodic CSI encoder whichselects, when the CSI request field is set to a request value, a DL CCaccording to a rule configured by a higher layer and DL CCidentification information included in the UL grant, measures thechannel state of the selected DL CC, and generates the CSI with themeasured channel state. The terminal additionally includes a transmitterthat transmits the CSI to the base station on the UL CC scheduled bymeans of the UL grant.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the presentinvention will be more apparent from the following detailed descriptionwhen taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram illustrating a relationship of the DL CC 100 and theUL CC 101 in the LTE Release 8 system;

FIG. 2 is a diagram illustrating a linkage relationship between DL CCsand UL CCs in the CSI request/feedback method, according to a firstembodiment of the present invention;

FIG. 3 is a flowchart illustrating an aperiodic CSI request/feedbackmethod between an eNB and a UE, according to the first embodiment of thepresent invention;

FIG. 4 is a diagram illustrating a linkage relationship between DL CCsand UL CCs in the CSI request/feedback method, according to a secondembodiment of the present invention;

FIG. 5 is a flowchart illustrating an aperiodic CSI request/feedbackmethod between an eNB and a UE, according to the second embodiment ofthe present invention;

FIG. 6 is a flowchart illustrating an aperiodic CSI request/feedbackmethod, according to a third embodiment of the present invention;

FIG. 7 is a diagram illustrating a linkage relationship between DL CCsand UL CCs in the CSI request/feedback method, according to a fourthembodiment of the present invention;

FIG. 8 is a flowchart illustrating an aperiodic CSI request/feedbackmethod, according to the fourth embodiment of the present invention;

FIG. 9 is a diagram illustrating a linkage relationship between DL CCsand UL CCs in the CSI request/feedback method, according to a fifthembodiment of the present invention;

FIG. 10 is a flowchart illustrating an aperiodic CSI request/feedbackmethod, according to the fifth embodiment of the present invention;

FIG. 11 is a block diagram illustrating a configuration of a UE forsupporting the CSI request/feedback method, according to an embodimentof the present invention;

FIG. 12 is a block diagram illustrating a configuration of an eNB forsupporting the CSI request/feedback method, according to an embodimentof the present invention;

FIG. 13 is a diagram illustrating a linkage relationship between DL CCsand UL CCs in the CSI request/feedback method, according to a sixthembodiment of the present invention;

FIG. 14 is a flowchart illustrating an aperiodic CSI request method ofan eNB, according to the sixth embodiment of the present invention; and

FIG. 15 is a flowchart illustrating an aperiodic CSI feedback method ofthe UE, according to the sixth embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

Embodiments of the present invention are described in detail withreference to the accompanying drawings. The same or similar componentsmay be designated by the same or similar reference numerals althoughthey are illustrated in different drawings. Detailed descriptions ofconstructions or processes known in the art may be omitted to avoidobscuring the subject matter of the present invention.

The dimensions of certain elements can be exaggerated or not in trueproportion. Also, the size of each element may not reflect the truesize.

A description is provided of the mobile terminal, according toembodiments of the present invention.

The description is made with terms related to carrier aggregationtechnology that are defined as following:

-   -   Backward compatible carrier: a carrier that the LTE UE also can        access    -   Non-backward compatible carrier: a carrier that only the LTE-A        UE can access    -   DL CC set: a set of downlink CCs    -   UL CC set: a set of uplink CCs    -   Carrier Indicator Field (CIF): a field indicating that, when it        is difficult to transmit the PDCCH on a certain component        carrier, the PDCCH is transmitted on another PDCCH and the PDCCH        indicates the PDSCH or PUSCH on another component carrier. Three        bits are added to the Downlink Control Information (DCI) format        so as to indicate another component carrier. The CIF is included        in the DCI format only in cases of cross carrier scheduling. The        DL CC is associated with a UL CC and the connection relationship        is transmitted by Radio Resource Control (RRC) signaling. When        the CIF is included in DL assignment, the CIF indicates the DL        CC on which the PDSCH, scheduled by the DL assignment, is        transmitted. When the CIF is included in the UL grant, the CIF        indicates the UL CC on which the PUSCH, scheduled by the UL        grant, is transmitted.

In the following description, the DL CC is used to denote the carrierfor transmitting control signal and/or data in DL. Also, the term UL CCis used to denote the carrier for transmitting control informationand/or data in UL.

In addition to the aforementioned terms, the terms “DL anchor CC,” “DLPrimary Component Carrier (PCC),” “UL anchor CC,” and “UL PPC” are alsoutilized herein. In embodiments of the present invention, thedescription is provided with the terms “DL anchor CC” and “UL anchorCC.” The DL anchor CC and UL anchor CC can be defined in view of the UE,and these CCs can be used for transmitting certain system informationand control information.

The DL CCs and UL CCs are linked. When the DCI format contains CIF, oneDL CC can be linked to multiple UL CCs or multiple DL CCs can be linkedto one UL CC. The CIF can indicate the UL CC transmitting PUSCH. Whenthe DCI format has no CIF, one DL CC should be linked to one UL CC.

The DL CC set is a set of downlink CCs defined by a cell. The DL CCsassigned to the UE are defined as some or all of the carriers includedin the DL CC set by RRC signaling. The different DL CCs can be assigneddepending on the UE.

Assuming that DL CC set={1, 2, 3, 4, 5} and each element of the DL CCset indicates a CC having a bandwidth of 20 MHz, the maximum number ofcarriers that can be assigned by a cell among the carriers contained inthe DL CC set is configured according to the device capability of theUE. For example, the network can assign DL CCs 1, 3, and 4, of which DLCC 3 is assigned as the DL anchor CC. Although it is assumed that theall of the CCs in the DL CC set have the same bandwidth in the aboveexample, embodiments of the present invention can be applied to the casewhere the CCs have different bandwidths.

FIG. 2 is a diagram illustrating a linkage relationship between DL CCs200, 201, 202, 203, and 204 and UL CCs 205, 206, and 207 in the CSIrequest/feedback method, according to the first embodiment of thepresent invention.

In the first embodiment of the present invention, cross carrierscheduling is supported. This means that the UL grant or the DLassignment includes CIF.

Referring to FIG. 2, DL CC1 200 is linked to UL CC1 205, UL CC2 206, andUL CC3 207, and the linkages are depicted by solid lines as shown inFIG. 2. On the DL CC1 200, both the UL grant and DL assignment can betransmitted. DL CC2 201, DL CC3 202, DL CC4 203, and DL CC5 204 are notlinked with any of the UL CCs, and no UL grant or DL assignment istransmitted on these DL CCs. Specifically, the DL CCs 201, 202, 203, and204 are used for the PDSCH, i.e., DL data transmission. The UL controlinformation about the DL CCs 201, 202, 203, and 204, i.e., ACK/NACK, canbe transmitted on the UL anchor CC defined by means of the RRCsignaling. An embodiment of the present invention relates to a procedurein which the eNB requests the UE for aperiodic channel state informationabout one of the DL CCs 201, 202, 203, and 204 and the UE measures andfeeds back the channel state information on the UL CC under theassumption of the linkages between the DL CCs and UL CCs, as shown inFIG. 2.

FIG. 3 is a flowchart illustrating an aperiodic CSI request/feedbackmethod between an eNB and a UE, according to the first embodiment of thepresent invention.

In the aperiodic CSI request/feedback method, according to the firstembodiment of the present invention, if the CSI request field is set to1, the CIF included in the UL grant indicates the DL CC for which theaperiodic channel state information is required rather than the UL CCfor PUSCH transmission. The CSI request procedure is described in detailwith reference to FIG. 3.

The eNB sets the CIF field to the index number of the DL CC of whichaperiodic CSI is necessary and the CSI request field of UL grant to 1 instep 300. The CIF is set to 2 for the aperiodic CSI of the DL CC2 201.The CIF is set to 3 for the aperiodic CSI of the DL CC3 202. The CIF isset to 4 for the aperiodic CSI of DL CC4 203. The CIF is set to 5 forthe aperiodic CSI of DL CC5 204. The CIF is set under the rule specifiedbetween the eNB and the UE.

The CSI request filed is used for identifying that the UL grant havingthe CSI request field is the UL grant having request for CSI. If the CSIrequest field is set to 1, this means that the UL grant is the signalrequesting for the CSI. Although it can be assumed that the CSI requestfield is set to 0 for the CSI request of the UL grant, the CSI requestfield is set to 1 for indicating the UL grant requesting for CSI inembodiments of the present invention. Since it is enough to carry theinformation with its value of 0 or 1, the CSI request field is assignedone bit. Nevertheless, more bits can be assigned for the CSI requestfield, according to an embodiment of the present invention, and in thiscase, the CSI request field can be set to a value other than 0 and 1 forindicating the UL grant requesting CSI.

In the following description, the expression “set the CSI request fieldto a request value” means that the CSI request field is set to a valueindicating the UL grant having request for CSI. In the followingdescription, the expression “the value of the CSI request field is therequest value” means that the CSI request field is set to a valueindicating the UL grant having request for CSI. In the following, if therequest value is 1, i.e. the CSI request field is set to 1, thisindicates the UL grant having a request for CSI.

According to another embodiment of the present invention, the field forindicating the DL CC, i.e. CIF assigned 3 bits for indicating the DL CCaccording to the first method using a predefined rule, can discriminateamong eight states such that, when there are 5 DL CCs as shown in FIG.2, five states can be used for indicating individual DL CCs and onestate for instructing feedback of CSIs of all the DL CCs. If the fielddefined for indicating the DL CC indicates a plurality of DL CCs, thismeans that the eNB requests for the aperiodic CSIs of the plural DL CCs.

According to the second method using a predefined rule for setting theCIF indicating the DL CC, the field for indicating the DL CC, i.e. CIFassigned 3 bits for indicating the DL CC, can discriminate among eightstates such that three states can be used for indicating individual DLCCs, other three states for indicating three possible pairs among the DLCCs, and one state for indicating all of the three DL CCs. For example,each bit for indicating each DL CC can be assigned to indicate whetherthe CSI of a certain DL CC is requested.

The predefined rule can be informed by RRC signaling or another method.

Referring again to FIG. 3, after setting the CIF, the eNB transmits theUL grant to the UE on the DL CC1 200, in step 310. At step 310, the eNBselects the DL CC supporting transmission of UL grant and DL assignmentand linked to the UL CCs. Since the CIF is used in order to indicate theDL CC of which aperiodic CSI is necessary, the DL CC on which the ULgrant having the CIF is selected according the aforementionedconditions.

The UE performs decoding on the DL CC1 200 to receive the UL grant andchecks that the CSI request field of the received UL grant is set to 1,in step 320. The UE also checks the CIF of the received UL grant toidentify the DL CC of which aperiodic CSI is requested.

Next, the UE measures the channel state of the DL CC of which aperiodicchannel state information is requested, in step 330. the CSI measurementon the DL CC can include extracting the information for feedback of theCSI from the information on the previously measured or saved CSI. Thiscan be applied in other embodiments of the present invention.

After the measurement of the channel state, the UE feeds back theaperiodic CSI on the UL CC linked with the DL CC1 200 on which the ULgrant has been transmitted or the UL CC selected according to apredefined rule among UL CCs linked to the DL CC1 200, in step 340.

The predefined rule can be as follows: if the DL CC1 200 is linked tomultiple UL CCs having different bandwidths, the UE can determine the ULCC for the transmission of the aperiodic CSI based on the length of theUL grant. If the DL CC1 200 is linked with multiple UL CCs having thesame bandwidth, the UE can determine the UL CC for the transmission ofthe aperiodic CSI by means of RRC signaling or other method. The othermethod is to transmit the aperiodic CSI on the UL anchor CC when the DLCC1 200 is linked to multiple UL CCs.

When the eNB requests for the aperiodic CSI about more than two DL CCs,it can be considered to perform joint coding on the CSI about more thantwo DL CCs, rather than encode the aperiodic CSIs of DL CCs individuallyin another embodiment of the present invention. When the aperiodic CSIsof more than two DL CCs are greater than 11 bits, Tail BitingConvolutional Code (TBCC) or Turbo Code can be used. When the aperiodicCSIs of the DL CCs are less than or equal to the 11 bits, (32, x) blockcode can be used, where x means information size.

Although the description of the first embodiment of the presentinvention is directed to the case where the DL CC of which aperiodic CSIis requested is in an activated state, this method can be applied forrequesting aperiodic CSI of the DL CC in a deactivated state. When thereis a deactivated DL CC among the DL CCs 201, 202, 203, and 204 depictedin FIG. 2, the eNB can request for the aperiodic CSI of the deactivatedDL CC such that the UE feeds back the aperiodic CSI of the deactivatedDL CC, according to the procedure described with reference to FIG. 3. Inthis case, however, the Radio Frequency (RF) of the deactivated DL CCcan be turned on or off according to whether the deactivated DL CC iscontiguous in a frequency domain. Accordingly, the aforementionedprocess is not required when the RF of the deactivated DL CC is turnedon, at step 330. However, if the RF of the deactivated DL CC is turnedoff, it is required to turn on the RF first to measure the CSI thedeactivated DL CC.

FIG. 4 is a diagram illustrating a linkage relationship between DL CCs400, 401, and 402 and UL CCs 403 and 404 in the CSI request/feedbackmethod, according to the second embodiment of the present invention.

In the second embodiment of the present invention, the cross carrierscheduling is not supported. This means that the UL grant and DLassignment include no CIF. Referring to FIG. 4, DL CC1 400 is linked toUL CC1 403, and DL CC2 401 is linked to UL CC2 404. The linkagerelationship is expressed by solid lines as shown in FIG. 4. Both the ULgrant and DL assignment can be transmitted on the DL CC1 400 and DL CC2401. The DL CC3 402 is not linked to any UL CC, only the DL assignmentcan be transmitted on the DL CC3 402. The UL control information aboutthe DL CC3 402, i.e. ACK/NACK, can be transmitted on the UL anchor CCdefined by RRC signaling. The linkage relationship depicted in FIG. 4 isa carrier arrangement appropriate for the case where there is largeamount of data to be transmitted on the DL CC.

FIG. 5 is a flowchart illustrating an aperiodic CSI request/feedbackmethod between an eNB and a UE, according to the second embodiment ofthe present invention.

In the aperiodic CSI request/feedback method, according to the secondembodiment of the present invention, the eNB transmits the UL grant onthe DL CC of which aperiodic CSI is necessary and on which actual the ULgrant transmission is not allowed, and the UE checks whether the CSIrequest in the received signal is set to 1. If it is set to 1, the UEdetermines that the signal is transmitted to request for the aperiodicCSI of the DL CC on which the signal is received rather than that thesignal is mis-received.

In the current LTE specification, the DCI format 0 for UL grant and theDCI format lA for DL assignment are the same length (payload size) andthus, a 1-bit flag is used to differentiate between the two formats.Accordingly, the blind decoding on the signal received through the DLCC, which is not allowed for UL grant transmission, can be performed atthe UE without any problem.

The eNB first sets the CSI request field of the UL grant to 1, in step500. Next, the eNB transmits the UL grant to the UE through DL CC 3 402of which aperiodic CSI is necessary, in step 510. Meanwhile, the UEperforms blind decoding on the DL CC2 402 to receive the UL grant,checks that the CSI request field of the UL grant is set to 1, andrecognizes that the UL grant is transmitted to request of the aperiodicchannel state information of the DL CC3 402, rather than that it ismis-received, in step 520. The UE measures the channel state of the DLCC3 402 of which aperiodic CSI is necessary, in step 530. Finally, theUE transmits the aperiodic CSI of the DL CC3 402, on which the UL grantis received, on the UL CC selected according to a predefined rule, instep 540. Here, the predefined rule can be as follows: the UL CC foraperiodic CSI transmission can be determined by RRC signaling or anothermethod, or the UL anchor CC can be selected for the aperiodic CSItransmission.

FIG. 6 is a flowchart illustrating an aperiodic CSI request/feedbackmethod, according to the third embodiment of the present invention.

In the third embodiment of the present invention, the description ismade with reference to the linkage relationship between the DL CCs andUL CCs as depicted in FIG. 2. As in the first embodiment, the crosscarrier scheduling is supported in the third embodiment, and the ULgrant and DL assignment include a CIF.

In the aperiodic CSI request/feedback method according to the thirdembodiment, a DL CC indicator or a UL CC indicator is added to the ULgrant for expressing whether the CIF of the UL grant is indicating a DLCC or a UL CC. The DL CC indicator or UL CC indicator can be assigned 1bit. In the following, the description is made under the assumption that1-bit DL CC indicator is added to the UL grant. Although the namediffers from the DL CC indicator, the UL CC indicator is basicallyidentical with the DL CC indicator in that it is used to indicatewhether the CIF of the UL grant indicates a DL CC or a UL CC.

The eNB first sets the DL CC indicator for reporting aperiodic CSI inthe UL grant, in step 600. The DL CC indicator is set to 1 for the CIFindicating a DL CC, and set to 0 for the CIF indicating a UL CC. Therecan be an embodiment in which the DL CC indicator is set to 0 for theCIF indicating a DL CC, and set to 1 for the CIF indicating a UL CC.When the UL CC indicator is used in place of the DL CC indicator, the ULCC indicator can be set in similar manner.

According to whether the DL CC indicator for requesting the aperiodicCSI is set to 1 or 0 in step 601, the process is branched to step 610 orstep 620. If the DL CC indicator is set to 1, this means that the CIFindicates a DL CC and the procedure goes to step 610 and, otherwise, theprocedure goes to step 620.

At step 610, the eNB sets the CIF of the UL grant to the index of the DLCC of which the aperiodic CSI is necessary and sets the CSI requestfield of the UL grant to 1. For example, the CIF is set to 2 forrequesting the aperiodic CSI of the DL CC2 201. The CIF is set to 3 forrequesting the aperiodic CSI of the DL CC3 202. The CIF is set to 4 forrequesting the aperiodic CSI of the DL CC4 203. The CIF is set to 5 forrequesting the aperiodic CSI of the DL CC5 204. The CIF setting methodfollows the rule specified between the eNB and the UE.

The field for indicating the DL CC, i.e., CIF assigned 3 bits forindicating the DL CC according to the first method using a predefinedrule, can discriminate among eight states such that, when there are 5 DLCCs, as shown in FIG. 2, five states can be used for indicatingindividual DL CCs and one state for instructing feedback of CSIs of allthe DL CCs. If the field defined for indicating the DL CC indicates aplurality of DL CC, this means that the eNB requests for the aperiodicCSIs of the plural DL CCs.

According to the second method using a predefined rule for setting theCIF indicating the DL CC, the field for indicating the DL CC, i.e. CIFassigned 3 bits for indicating the DL CC, can discriminate among eightstates such that three states can be used for indicating individual DLCCs, another three states can be used for indicating three possiblepairs among the DL CCs, and one state can be used for indicating all ofthe three DL CCs. Each bit for indicating each DL CC can be assigned toindicate whether the CSI of a certain DL CC is requested.

The present rule can be informed by RRC signaling or another method.

Referring again to FIG. 6, after setting the CIF, the eNB transmits theUL grant on the DL CC selected among the DL CCs linked to the UL CC, instep 611. In FIG. 2, the eNB transmits the UL grant to the UE on the DLCC1 200. Both the UL grant and DL assignment can be transmitted, and theDL CC linked to the UL CC can be selected for transmitting the UL grant.Since the CIF is used for indicating the DL CC of which aperiodic CSI isrequested, the DL CC for transmitting the UL grant containing the CIFcan be selected based on the aforementioned condition.

The UE performs blind decoding on the DL CC to receive the UL grant, instep 612. The UE checks that the CSI request field of the UL grant isset to 1. The UE can recognize that the received UL grant is the signalrequesting for the CSI. The UE extracts the DL CC indicator from thereceived UL grant. Since the DL CC indicator of the UL grant is set to1, the UE can identify the DL CC of which aperiodic CSI is requestedfrom the CIF of the received UL grant. If the DL CC indicator of the ULgrant is set to 0, a process, as in step 622, is performed. This processis described in greater detail below.

After receiving the UL grant, the UE measures the CSI of the DL CCindicated by the UL grant, in step 613. The DL CC of which CSI isrequested can be identified using the CIF as described above.

The UE transmits the aperiodic CSI on the UL CC linked to the DL CC onwhich the UL grant is transmitted, or the UL CC selected among the ULCCs linked to the DL CC according to the predefined rule, in step 614.Here, the predefined rule can be as follows:

If the DL CC is linked to a plurality of UL CCs having differentbandwidths, the UE can determine the UL CC for transmitting theaperiodic CSI based on the length of the UL grant. If the DL CC islinked to a plurality of UL CCs having the same bandwidth, the UE candetermine the UL CC for transmitting the aperiodic CSI by RRC signalingor another method. The other method is to transmit the aperiodic CSI onthe UL anchor CC when the DL CC is linked to multiple UL CCs.

Returning to step 601, if the DL CC indicator is set to 0, this meansthat the CIF indicates a UL CC. When the CIF indicates a UL CC, the DLCC of which aperiodic CSI is necessary should be linked to the UL CC. Ifthe DL CC indicator is set to 0, the procedure goes to step 620.

At step 620, the eNB sets the CIF of the UL grant to the index of the ULCC on which the UE transmits PUSCH and sets the CSI of the UL grantto 1. The eNB transmits the UL grant to the UE through the DL CC ofwhich aperiodic CSI is requested, in step 621. In FIG. 2, the eNB cantransmit the UL grant to the UE on the DL CC1 200 for receiving theaperiodic CSI of the DL CC1 200. Only the DL CC1 200 is linked to the ULCCs.

The UE performs blind decoding on the DL CC to receive the UL grant, instep 622. The UE checks that the CSI request field of the UL grant isset to 1. By checking the CSI request field set of the UL grant that isset to 1, the UE can identify that the received UL grant of requestingCSI. The UE extracts the DL CC indicator of the UL grant. The UE cancheck that the DL CC indicator is set to 0. Accordingly, the UE canidentify the UL CC for transmitting PUSCH based on the CIF of the ULgrant.

The UE measures the channel state of the DL CC of which aperiodic CSI isrequested, in step 623. As described above, the DL CC on which the ULgrant is transmitted is the DL CC of which CSI is requested.

The UE transmits the aperiodic CSI through the UL CC which is supposedto transmit PUSCH, i.e. the UL CC indicated by the CIF, in step 624.

In the third embodiment of the present invention described withreference to FIG. 6, an indicator is provided for expressing whether theCIF indicates a DL CC or a UL CC. In this manner, this embodiment of thepresent invention is capable of requesting and feeding back an aperiodicCSI in the system supporting carrier aggregation unlike the conventionLTE system, in which the aperiodic CSI request/feedback is impossible.When a certain DL CC is supported by the conventional LTE standard, theCIF is used to indicate the UL CC for transmitting the CSI, so as tosupport the aperiodic CSI request/feedback.

Although the description made with reference to FIG. 6 is directed tothe case of aperiodic CSI request/feedback of the already activated ULCC, the CSI request/feedback method of the present invent can be appliedfor aperiodic CSI request/feedback for DL CC in a deactivated state. Ifthere is a DL CC deactivated among the DL CCs 201, 202, 203, and 204 inFIG. 2, the DL CC indicator is set such that the CIF indicates the DL CCaccording to the procedure of FIG. 6. The eNB requests the aperiodic CSIof the deactivated DL CC, and the UE can transmit the aperiodic CSI ofthe deactivated DL CC. In this case, however, the RF of the deactivatedDL CC can be turned on or off according to whether the deactivated DL CCis contiguous or not in the frequency domain. When the RF of thedeactivated DL CC is turned on, step 613 is performed as shown in FIG.6. However, when the RF of the deactivated DL CC is turned off, it isrequired to turn on the RF before measuring the channel state of thedeactivated DL CC.

FIG. 7 is a diagram illustrating a linkage relationship between DL CCsand UL CCs in the CSI request/feedback method, according to the fourthembodiment of the present invention. In the fourth embodiment of thepresent invention, the cross carrier scheduling is supported.Specifically, both the UL grant and DL assignment include a CIF. Adescription is provided below of the linkage relationship in detail.

Referring to FIG. 7, DL CC1 700 is linked to UL CC1 703, UL CC2 704, ULCC3 705, and UL CC4 706, and the linkage relationship is expressed by asolid line. Both the UL grant and DL assignment can be transmitted onthe DL CC1 700. The description below is directed to the case where DLCC2 701 and DL CC3 702 are not linked to any UL CC, and the UL grant andDL assignment of the DL CC2 701 and DL CC3 702 are not transmitted. Thismeans that the DL CC2 701 and DL CC3 702 are used in the PDSCH, i.e.downlink data. The UL control information, i.e. ACK/NACK, for the DL CC2701 and DL CC3 702 can be transmitted on a UL anchor CC defined by RRCsignaling.

FIG. 8 is a flowchart illustrating an aperiodic CSI request/feedbackmethod, according to the fourth embodiment of the present invention.

In the aperiodic CSI request/feedback method according to the fourthembodiment of the present invention, the value that is not used as theUL CC indicator among the CIF values of the UL grant is used forindicating the DL CC of which aperiodic CSI is necessary. Specifically,since the CIF values that can be used as the UL CC identifier are 1, 2,3, and 4, the rest values of 5, 6, 7, and 8 are used for indicating theDL CC2 and DL CC3. In the above example, the CIF value of 5 can be usedfor indicating the DL CC2 701 and the CIF value of 6 for indicating theDL CC3 702. When the CIF of the UL grant transmitted by the eNB is setto a value indicating a DL CC, the UE receives the UL grant and checksthat the CSI request field of the UL grant is set to 1 and thus, the CIFof the UL grant is set to 5 or 6. The CIF value of 5 or 6 can benegotiated to be used as a DL CC indicator between the eNB and UE.Accordingly, the UE can recognize that the CIF of the UL grant which hasthe value of 5 or 6 is not used as the indicator of the UL CC fortransmitting PUSCH but as the indicator of the DL CC of which aperiodicCSI is requested.

Referring to FIG. 8, the eNB first sets the CSI request field of the ULgrant to 1, in step 800. At step 800, the eNB also sets the CIF of theUL grant to a CIF value assigned as the indicator of the DL CC of whichaperiodic CSI is necessary. The CIF value assigned as an indicator of DLCC can be a value predefined among CIF values that are not assigned asindicators of UL CCs. For example, the eNB can assign the value of 5 asthe indicator of the DL CC2 and the valued of 6 as the indicator of theDL CC3 and notify the UE of DL CC indicator values by RRC signaling orother method. In FIG. 7, the eNB can set the CIF to 5 to request for theaperiodic CSI of the DL CC2 701, or can set the CIF to 6 to request theaperiodic CSI of the DL CC3 702.

As in the first and third embodiments of the present invention, it ispossible to request the CSI of plural DL CCs with one of the CIF states.In the fourth embodiment of the present invention, however, the numberof CIF states may be shortened such that the combined CSI request formultiple DL CCs is limited to some extent.

Next, the eNB transmits the UL grant to the UE on the DL CC1 700 linkedto the UL CC, in step 810. Both the UL grant and DL assignment can betransmitted, and the DL CC linked to the UL CC is selected fortransmitting the UL grant. Since the CIF is used to indicate the DL CCof which aperiodic CSI is necessary, the DL CC for transmitting the ULgrant containing the CIF can be selected according to the aforementionedconditions.

Meanwhile, the UE performs blind decoding on the DL CC1 700 to receivethe UL grant, in step 820. At step 820, the UE analyzes the CSI requestfield of the UL grant so as to identify the received UL grant as a CSIrequest signal. The UE analyzes the CIF. Since the CIF is set to 5 or 6,the UE regards the CIF value as the indicator of the DL CC of whichaperiodic CSI is requested. Accordingly, the UE can identify the DL CCof which aperiodic CSI is requested, based on the CIF value.

Next, the UE measures the channel quality of the DL CC of whichaperiodic CSI is requested, in step 830. Specifically, the UE measuresthe channel quality of the DL CC indicated by the CIF of the UL grant.

Finally, the UE transmits the aperiodic CSI on UL CC linked to the DLCC1 700 on which the UL grant is transmitted or the UL CC selectedaccording to the reset rule among the UL CCs linked to the DL CC1 700,in step 840. The predefined rule is as follows:

If the DL CC is linked to a plurality of UL CCs having differentbandwidths, the UE can determine the UL CC for transmitting theaperiodic CSI based on the length of the UL grant. If the DL CC islinked to a plurality of UL CCs having the same bandwidth, the UE candetermine the UL CC for transmitting the aperiodic CSI by RRC signalingor another method. The other method is to transmit the aperiodic CSI onthe UL anchor CC when the DL CC is linked to multiple UL CCs.

When the eNB requests the aperiodic CSIs of two or more DL CCs, it canbe considered to perform joint coding on the CSI about more than two DLCCs rather than encode the aperiodic CSIs of DL CCs individually inanother embodiment of the present invention. When the aperiodic CSIs ofmore than two DL CCs are greater than 11 bits, TBCC or Turbo Code can beused. When the aperiodic CSIs of the DL CCs are less than or equal tothe 11 bits, (32, x) block code can be used, where x means informationsize.

Although the aperiodic CSI request/feedback method described withreference to FIGS. 7 and 8 have been directed to the case of requestingthe aperiodic CSI of the already activated DL CC, it can be applied tothe case of requesting aperiodic CSI of a deactivated DL CC. If there isa deactivated DL CC among the DL CCs 701 and 702 in FIG. 7, the eNB canrequest the UE for the aperiodic CSI of the deactivated DL CC, and thus,the UE transmits the aperiodic CSI of the deactivated DL CC. In thiscase, however, the RF of the deactivated DL CC can be turned on or offaccording to whether the deactivated DL CC is contiguous in thefrequency domain. When the RF of the deactivated DL CC is turned on,step 830 is performed as shown in FIG. 6, but when the RF of thedeactivated DL CC is turned off, it is required to turn on the RF beforemeasuring the channel state of the deactivated DL CC.

FIG. 9 is a diagram illustrating a linkage relationship between DL CCsand UL CCs in the CSI request/feedback method, according to the fifthembodiment of the present invention.

In the fifth embodiment of the present invention, the cross carrierscheduling is not supported. Specifically, the UL grant and DLassignment carry no CIF. Referring to FIG. 9, DL CC1 900 is linked to ULCC1 905, and DL CC3 902 is linked to the UL CC2 906. The linkagerelationships are expressed by solid lines in FIG. 9. The DL CC1 900 andDL CC3 902 can be used for transmitting the UL grant and DL assignment.Meanwhile, DL CC2 901, DL CC4 903, and DL CC5 904 are not linked to anyUL CC, and it is assumed that only the DL assignment transmission isallowed. The UL control information, i.e. ACK/NACK, for the DL CCs 901,903, and 904 that are not supporting transmission of UL grant, can betransmitted on the UL anchor CC defined by RRC signaling. The linkagerelationship depicted in FIG. 9 is a carrier arrangement available forcase where there is a large amount of data to be transmitted indownlink.

FIG. 10 is a flowchart illustrating an aperiodic CSI request/feedbackmethod, according to the fifth embodiment of the present invention.

In the aperiodic CSI request/feedback method according to the fifthembodiment of the present invention, 3 bits for indicating the DL CC canbe added to the UL grant or, when the CSI request is set to 1, at leastone field currently reserved for another purpose in the UL grant can beused for indicating DL CC. The new 3 bits can be added by newly definingthe UL grant for UL transmission, and the at least one field reservedfor other purpose includes 3-bit cyclic shift for Demodulation ReferenceSignal (DMRS), 1-bit hoping flag, 1-bit New Data Indicator (NDI), and2-bit Transmission Power Control (TPC) command. In the LTE Release 8specification, if the CSI request field is set to 1 with Modulation andCoding Scheme (MCS) level of 29 and the Physical Resource Blocks (PRBs)of which number equal to or less than 4, no transport block istransmitted. Accordingly, it can be possible to use bit fields forindicating the DL CC of which aperiodic CSI is necessary.

In the following, the description is made of the aperiodic channelrequest/feedback procedure under the assumption that there is a bitfield negotiated for use in indicating DL CC according to theaforementioned method.

The aperiodic channel request/feedback procedure depicted in FIG. 10 canbe applied to the system implemented with the component carrierconfiguration as depicted in FIG. 2 as well as FIG. 9. The detaileddescription is provided below.

The eNB first sets the CSI request field of the UL grant to 1 and sets afield selected for indicating the DL CC in the UL grant to a valueindicating the DL CC of which aperiodic CSI is necessary according to apredefined rule in step 1000.

In the first method for setting the field indicating the DL CC based ona predefined rule, if 3 bits are assigned for indicating DL CC, it ispossible to discriminate among eight states with the 3 bits such that,when there are 5 DL CCs as shown in FIGS. 2 and 9, five states can beused for indicating individual DL CCs and one state for instructingfeedback of CSIs of all the DL CCs. If the field defined for indicatingthe DL CC indicates a plurality of DL CCs, this means that the eNBrequests the aperiodic CSIs of the plural DL CCs.

In the second method for setting the field indicating the DL CC based ona predefined rule, if 3 bits are assigned for indicating DL CC, it ispossible to discriminate among eight states with the 3 bits such that,when there are 3 DL CCs as shown in FIG. 4, three states can be used forindicating individual DL CCs, another three states can be used forindicating three possible pairs among the DL CCs, and one state can beused for indicating all of the three DL CCs. For example, each bit forindicating each DL CC can be assigned to indicate whether the CSI of acertain DL CC is requested.

The predefined rule can be informed by RRC signaling or another method.

If there exists the CIF as in the embodiment described in FIG. 2, theeNB uses the CIF as an identifier of the UL CC for transmission ofPUSCH.

Referring again to FIG. 10, the eNB transmits the UL grant to the UE onthe DL CC, in step 1010. If there is the CIF as in the case of FIG. 2,the eNB transmits the UL grant on the DL CC linked to the UL CCidentified by the CIF. Otherwise, if no CIF exist as in the case of FIG.9, it is possible to transmit the UL grant and DL assignment. The ULgrant is transmitted on the DL CCs linked to the UL CC, i.e., the DL CC1900 or DL CC3 902.

The UE performs blind decoding on the DL CC to receive the UL grant andchecks that the CSI request field is set to 1, in step 1020. At step1020, the UE also identifies the DL CC of which aperiodic CSI isrequested based on specific bits of the UL grant that are negotiated forindicating the DL CC according to the predefined rule. The predefinedrule is the predefined rule described at step 1000 and transmitted fromthe eNB to the UE by RRC signaling or other method.

The UE measures the channel quality of the DL CC of which aperiodic CSIis necessary, in step 1030. The DL CC of which aperiodic CSI isnecessary is the one identified by analyzing the field negotiated forindicating the DL CC at step 1020.

The UE transmits the aperiodic CSI of the DL CC through the UL CC, instep 1040. If there is the CIF as in the case of FIG. 2 at step 1030,the UE transmits the aperiodic CSI of the DL CC on the UL CC identifiedby the CIF. Otherwise, if there is no CIF as in the case of FIG. 9, theUE transmits the aperiodic CSI of the DL CC through the UL CC linked tothe DL CC on which the UL grant is received or a UL anchor CC.

When the eNB requests the aperiodic CSIs of two or more DL CCs, it canbe considered to perform joint coding on the CSI about more than two DLCCs rather than encode the aperiodic CSIs of DL CCs individually inanother embodiment of the present invention. When the aperiodic CSIs ofmore than two DL CCs are greater than 11 bits, TBCC or Turbo Code can beused. When the aperiodic CSIs of the DL CCs are equal to or less thanthe 11 bits, (32, x) block code can be used, where x means informationsize.

Although the aperiodic CSI request/feedback method described withreference to FIG. 10 has been directed to the case of requesting theaperiodic CSI of the already activated DL CC, it can be applied to thecase of requesting aperiodic CSI of a deactivated DL CC. If there is adeactivated DL CC among the DL CCs in FIG. 2 or 9, the eNB can requestthe UE for the aperiodic CSI of the deactivated DL CC as described withreference to FIG. 10, and thus, the UE can transmit the aperiodic CSI ofthe deactivated DL CC. In this case, however, the RF of the deactivatedDL CC can be turned on or off according to whether the deactivated DL CCis contiguous or not in frequency domain. In the state where the RF ofthe deactivated DL CC is turned on, step 830 is performed as shown inFIG. 8, but when the RF of the deactivated DL CC is turned off, it isrequired to turn on the RF before measuring the channel state of thedeactivated DL CC.

FIG. 11 is a block diagram illustrating a configuration of a UE forsupporting the CSI request/feedback method, according to an embodimentof the present invention.

A receiver 1100 receives the UL grant according to one of theembodiments of the present invention and delivers the UL grant to aPDCCH decoder 1101. The PDCCH decoder 1101 decodes and analyzes the ULgrant so as to extract the value from the CSI request field or a certainfield added to the UL grant, according to an embodiment of the presentinvention. Based on the field value and other information, it ispossible to identify the DL CC of which aperiodic channel is requestedand the UL CC for transmitting the aperiodic CSI, according to one ofthe embodiments of the present invention. An aperiodic CSI decoder 1102generates the aperiodic CSI of the DL CC, and a PUSCH encoder 1103generates uplink data information. The DL CC aperiodic CSI generated bythe aperiodic CSI decoder 1102 and the uplink data information generatedby the PUSCH encoder 1103 is multiplexed by a multiplexer 1104 and thentransferred to a transmitter 1105. The transmitter 1105 transmits themultiplexed data to the eNB.

FIG. 12 is a block diagram illustrating a configuration of an eNB forsupporting the CSI request/feedback method, according to an embodimentof the present invention.

A scheduler 1200 and a controller 1201 control a PDCCH generator 1202 togenerate the UL grant, according to one of the embodiments of thepresent invention, and transfer the UL grant to a transmitter 1203. Asdescribed above, the UL grant includes the indicator indicating arequest for aperiodic CSI. The transmitter 1203 transmits the UL grantprovided by the PDCCH generator 1202 to the UE. The scheduler 1200 andcontroller 1201 also control a receiver 1204 to receive the uplinkinformation, according to one of the embodiments of the presentinvention, and to transfer the uplink information to a demultiplexer1205. The demultiplexer 1205 demultiplexes the uplink information intouplink data information and aperiodic CSI, and transfers the aperiodicCSI to an aperiodic CSI decoder 1206, and transfers the uplink datainformation to a PUSCH decoder 1207. The aperiodic CSI decoder 1206decodes the aperiodic CSI, and the PUSCH decoder 1207 decodes the uplinkdata information.

FIG. 13 is a diagram illustrating a linkage relationship between DL CCs1300, 1301, 1302, 1303, and 1304 and UL CCs 1304, 1306, and 1307 in theCSI request/feedback method, according to the sixth embodiment of thepresent invention.

In the sixth embodiment of the present invention, the cross carrierscheduling is supported. Specifically, the UL grant and DL assignmentinclude a CIF.

Referring to FIG. 13, the DL CC and UL CC of each pair of DL CC1 1300and UL CC1 1305, DL CC2 1301 and UL CC2 1306, and DL CC3 1302 and UL CC31307 are linked via an SIB link. DL CC4 1303 and DL CC5 1304 are notlinked to any UL CC. The SIB link is expressed by a shadow line toindicate the systematic linkage between the DL CCs and UL CCs by thesystem information. Since the cross scheduling is allowed, it is notedthat the scheduling for the UL CC may not occur on the DL CC linked viaSIB link. Although the description is made under the assumption that theDL CC4 1303 and DL CC5 1304 are not linked to any UL CC via an SIB link,an embodiment where the DL CC is associated with a UL CC through an SIBlink is described separately. In FIG. 13, the scheduling relationship isexpressed by a solid line arrow. While the solid line used forexpressing the linkage relationship between a DL CC and a UL CC in FIGS.2 and 7 means the relationship between the DL CC for transmitting the ULgrant and the UL CC for transmitting the PUSCH scheduled by the ULgrant, the solid line arrow is used to express the same relationship inthis embodiment. The DL CC1 1300 can be used to transmit both the ULgrant and DL assignment, while other DL CCs 1301, 1302, 1303, and 1304are not used to transmit UL grant and DL assignment. This means that theDL CCs 1301, 1302, 1303, and 1304 are used for transmitting only thePDSCH, i.e. downlink data. The UL control information, i.e. ACK/NACK,for the DL CCs 1301, 1302, 1303, and 1304 can be transmitted on the ULanchor CC defined by RRC signaling.

The CSI request procedure in which an eNB requests a UE for theaperiodic CSI of one of the DL CCs 1301, 1302, 1303, and 1304 and theCSI feedback procedure in which the UE measures and feeds back the CSIto the eNB are described with reference to FIGS. 14 and 15,respectively, under the assumption of the linkage relationship betweenthe DL CCs and UL CCs depicted in FIG. 13.

A description is made of the procedure for requesting for aperiodic CSIa certain DL CC according to the sixth embodiment hereinafter. The DL CCof which aperiodic CSI is requested with the CIF request field set to 1is configured as the DL CC linked to the UL CC indicated by the CIFfield via SIB link. This is described in more detail with reference toFIGS. 14 and 15.

FIG. 14 is a flowchart illustrating an aperiodic CSI request method ofan eNB, according to the sixth embodiment of the present invention.

The eNB first transmits a rule predefining the relationship fordetermining the CIF field value of the UL grant and the DL CC of whichaperiodic CSI is requested to the UE, in step 1400. According to thepredefined rule, the CIF value for requesting for the aperiodic CSI ofthe DL CCs that has no SIB link with any UL CC in FIG. 13 can bedetermined. Since it is assumed that the DL CC4 1303 and the DL CC5 1304have no SIB link with any UL CC in FIG. 13, when the CIF of the UL grantis set to a value indicating the UL CC1 1305, the aperiodic CSI of theDL CC4 1303 can be transmitted in addition to the DL CC1 1300 which isSIB-linked with the UL CC1 1305. When the CIF of the UL grant is set toa value indicating the UL CC2 1306, the aperiodic CSI of the DL CC5 1304can be transmitted in addition to the DL CC2 1301 which is SIB linkedwith the UL CC2 1306. Also, when the CIF of the UL grant is set to avalue indicating the UL CC3 1307, it is possible to transmit theaperiodic CSIs of the DL CC4 1303 and DL CC5 1304 in addition to the DLCC3 1302 which is SIB-linked to the UL CC3 1307. Although thedescription has been made under the assumption that the DL CC4 1303 andthe DL CC5 1304 are not SIB-linked with any UL CC, if the DL CC4 1303and the DL CC5 1304 are SIB-linked with any UL CC, e.g. the UL CC3 1307is SIB-linked with DL CC3 1302, DL CC4 1303, and DL CC5 1304, it is notnecessary to transmit the predefined rule to the UE. When it isnecessary to provide the predefined rule to the UE, the predefined rulecan be informed by higher layer signaling such as RRC signaling or canbe transmitted in system information.

When the aperiodic CSI of a specific DL CC is necessary, the eNB setsthe CIF of the UL grant to a certain value and sets the CSI requestfield to 1, according to the predefined rule, in step 1410. In theconfiguration of FIG. 13, the eNB sets the CIF to 2 for the aperiodicCSI of the DL CC2 1301, sets the CIF to 3 for the aperiodic CSI of theDL CC3 1302, a value selected according to the predefined rule for theaperiodic CSI of the DL CC4 1303, and sets the CIF to another valueselected according to the predefined rule for the aperiodic CSI of theDL CC5 1304.

The eNB transmits the UL grant to the UE on the DL CC1 1300, in step1420. At step 1420, the eNB also selects the DL CC available fortransmitting the UL grant for the UL CC, which is SIB-linked to the DLCC of which aperiodic CSI is necessary. Since the aperiodic CSI of theDL CC that is SIB-linked to the UL CC indicated by the CIF istransmitted, the DL CC on which the UL grant including the CIF istransmitted can be selected according to the aforementioned conditions.

Finally, the eNB receives the aperiodic CSI included in the PUSCH, whichthe UE has transmitted on the UL CC indicated by the CIF field value, instep 1430.

FIG. 15 is a flowchart illustrating an aperiodic CSI feedback method ofthe UE, according to the sixth embodiment of the present invention.

The UE first receives the rule predefining the relationship fordetermining CIF field value of the UL grant and the DL CC of whichaperiodic CSI is requested for the eNB, in step 1500.

The predefined rule is identical with that transmitted by the eNB atstep 1400 of FIG. 14 and, when all of the DL CCs are SIB-linked to an ULCC, it is not necessary for the eNB to transmit the predefined rule tothe UE.

The UE performs blind decoding on the DL CC1 1300 to receive the ULgrant and checks the CSI request field of the received UL grant which isset to 1, in step 1510. The UE identifies the DL CC of which aperiodicCSI is requested based on the CIF field of the received UL grant and thepredefined rule.

The UE measures the channel quality of the DL CC of which aperiodic CSIis requested, in step 1520. Measuring the CSI of the DL CC can includethe operation of extracting the information for transmitting the CSIthat is measured and stored already. This can be applied in otherembodiments.

The UE transmits the aperiodic CSI on the UL CC indicated by the CIFfield value of the UL grant, in step 1530.

When the eNB requests for the aperiodic CSIs of two or more DL CCs, itcan be considered to encode the aperiodic CSIs of more than two DL CCsindividually and then multiplex the coded aperiodic CSIs. When theaperiodic CSIs of more than two DL CCs are greater than 11 bits, TBCC orTurbo Code can be used. When the aperiodic CSIs of the DL CCs are equalto or less than the 11 bits, (32, x) block code can be used, where xmeans information size.

Although the aperiodic CSI request/feedback method according to thesixth embodiment has been directed to the case of requesting theaperiodic CSI of the already activated DL CC, it can be applied to thecase of requesting aperiodic CSI of a deactivated DL CC. If there is adeactivated DL CC among the DL CCs 201, 202, 203, and 204 in FIG. 2, theeNB can request the UE for the aperiodic CSI of the deactivated DL CCaccording to the procedure of FIG. 14, and the UE transmits theaperiodic CSI of the deactivated DL CC according to the procedure ofFIG. 15. In this case, however, the RF of the deactivated DL CC can beturned on or off according to whether the deactivated DL CC iscontiguous in the frequency domain. In the state where the RF of thedeactivated DL CC is turned on, the procedure is performed as shown inFIG. 6, but when the RF of the deactivated DL CC is turned off, it isrequired to turn on the RF before measuring the channel state of thedeactivated DL CC.

Although the descriptions have been directed to the case where the eNBrequests the CSI with UL grant, the eNB can request the UE for the CSIwith a message equivalent to the uplink grant.

As described above, the CSI request/feedback method and apparatus of thepresent invention enables the eNB to request aperiodic CSI of a DL CCand the UE to measure and feed back the aperiodic CSI of the DL CCthrough the UL CC in the wireless communication system adopting thebandwidth extension technique.

It should be appreciated that the steps of the flowchart and theircombinations can be implemented in the form of computer-readable programinstructions. The computer program instructions may also be loaded ontoa universal computer, a special-purpose computer, or other programmabledata processing apparatus to cause a series of operational steps to beperformed on the computer or other programmable apparatus to produce acomputer-implemented process. The instructions that execute on thecomputer or other programmable apparatus provide steps for implementingthe functions specified in the flowchart block or blocks. Accordingly,blocks of the block diagrams and flowchart illustrations supportcombinations of means for performing the specified functions,combinations of steps for performing the specified functions and programinstruction means for performing the specified functions. It will alsobe understood that each block of the block diagrams and flowchartillustrations, and combinations of blocks in the block diagrams andflowchart illustrations, can be implemented by special purposehardware-based computer systems that perform the specified functions orsteps, or combinations of special purpose hardware and computerinstructions.

The block diagrams in the figures illustrate the architecture,functionality, and operation of possible implementations of systems,methods and computer program products according to various embodimentsof the present invention. In this regard, each block in the blockdiagrams may represent a module, segment, or portion of code, whichcomprises one or more executable instructions for implementing thespecified logical function(s). It should also be noted that thefunctions noted in the blocks may occur out of the order noted in thefigures. For example, two blocks shown in succession may, in fact, beexecuted substantially concurrently, or the blocks may sometimes beexecuted in the reverse order, depending upon the functionalityinvolved. It will also be noted that each block of the block diagramscan be implemented by special purpose hardware-based systems thatperform the specified functions or acts, or combinations of specialpurpose hardware and computer instructions.

The term “module” according to the embodiments of the invention, means,but is not limited to, a software or hardware component, such as a FieldProgrammable Gate Array (FPGA) or Application Specific IntegratedCircuit (ASIC), which performs certain tasks. A module mayadvantageously be configured to reside on the addressable storage mediumand configured to be executed on one or more processors. Thus, a modulemay include, by way of example, components, such as software components,object-oriented software components, class components and taskcomponents, processes, functions, attributes, procedures, subroutines,segments of program code, drivers, firmware, microcode, circuitry, data,databases, data structures, tables, arrays, and variables. Thefunctionality provided for in the components and modules may be combinedinto fewer components and modules or further separated into additionalcomponents and modules. In addition, the components and modules may beimplemented such that they execute one or more CPUs in a device or asecure multimedia card.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

Although embodiments of the present invention have been described indetail with specific terminology, this is for the purpose of describingparticular embodiments only and not intended to be limiting of theinvention. While the invention has been shown and described withreference to certain embodiments thereof, it will be understood by thoseskilled in the art that various other changes in form and detail may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims.

1. A Channel State Information (CSI) request method of a base station,comprising the steps of: setting a CSI request field of an Uplink (UL)grant for scheduling a UL transmission on a UL Component Carrier (CC)corresponding to a Downlink (DL) CC of which CSI is requested, to arequest value; and transmitting the UL grant to a terminal.
 2. The CSIrequest method of claim 2, wherein setting the CSI request fieldcomprises setting the CSI request field of the UL grant for schedulingthe UL transmission on the UL CC that is SIB-linked with the DL CC ofwhich the CSI is requested, to the request value.
 3. The CSI requestmethod of claim 1, wherein setting the CSI request field comprisessetting a Carrier Indicator Field (CIF) of the uplink grant to anidentifier of the UL CC corresponding to the DL CC of which CSI isrequested.
 4. A based station for requesting a terminal for a ChannelState Information (CSI), comprising: a scheduler that sets a CSI requestfield of an Uplink (UL) grant for scheduling a UL transmission on a ULComponent Carrier (CC) corresponding to a Downlink (DL) CC of which CSIis requested, to a request value; and a transmitter that transmits theUL grant to the terminal.
 5. The base station of claim 4, wherein thescheduler sets the CSI request field of the UL grant for scheduling theUL transmission on the UL CC that is SIB-linked with the DL CC of whichCSI is requested, to the request value.
 6. The base station of claim 4,wherein the scheduler sets a Carrier Indicator Field (CIF) of the uplinkgrant to an identifier of the UL CC corresponding to the DL CC of whichCSI is requested.
 7. A Channel State Information (CSI) feedback methodof a terminal, comprising the steps of: receiving an Uplink (UL) grantfrom a base station; analyzing a CSI request field of the UL grant; whenthe CSI request field is set to a request value, generating a CSI of aDownlink Component Carrier (DL CC) corresponding to an UL CC scheduledby means of the UL grant by measuring a channel state of the DL CC; andfeeding back the CSI to the base station on the UL CC scheduled by meansof the UL grant.
 8. The CSI feedback method of claim 7, whereingenerating the CSI comprises measuring the channel state of the DL CCwhich is SIB-linked with the UL CC scheduled by means of the UL grant.9. The CSI feedback method of claim 7, wherein generating the CSIcomprises measuring the channel state of the DL CC corresponding to theUL CC indicated by a Carrier Indicator Field (CIF) of the UL grant. 10.A terminal for feeding back a Channel State Information (CSI) to a basestation, comprising: a receiver that receives an Uplink (UL) grant fromthe base station; a Physical Downlink Control Channel (PDCCH) decoderthat decodes a Channel State Information (CSI) request field of the ULgrant; an aperiodic CSI encoder that measures a channel state of aDownlink Component Carrier (DL CC) corresponding to an UL CC scheduledby means of the UL grant and generates a CSI with the measured channelstate, when the CSI request field is set to a request value; and atransmitter that transmits the CSI to the base station on the UL CCscheduled by means of the UL grant.
 11. The terminal of claim 10,wherein the aperiodic CSI decoder measures the channel state of the DLCC that is SIB-linked with the UL CC scheduled by means of the UL grant.12. The terminal of claim 10, wherein the aperiodic CSI decoder measuresthe channel state of the DL CC corresponding to the UL CC indicated by aCarrier Indicator Field (CIF) of the UL grant.
 13. A Channel StateInformation (CSI) request method of a terminal, comprising the steps of:configuring an Uplink (UL) grant having a CSI request field set to arequest value and an identifier of a Downlink Component Carrier (DL CC)of which CSI is requested, wherein the identifier is set according to arule configured by a higher layer; and transmitting the uplink grant tothe terminal.
 14. The CSI request method of claim 13, whereinconfiguring the UL grant comprises setting a Carrier Indicator Field(CIF) of the UL grant to the identifier of the DL CC of which the CSI isrequested.
 15. A base station for requesting a terminal for ChannelState Information (CSI), comprising: a scheduler that configures anUplink (UL) grant having a CSI request field set to a request value andan identifier of a Downlink Component Carrier (DL CC) of which CSI isrequested, wherein the identifier is set according to a rule configuredby a higher layer; and a transmitter that transmits the UL grant to theterminal.
 16. The base station of claim 15, where the scheduler sets aCarrier Indicator Field (CIF) of the UL grant to the identifier of theDL CC of which the CSI is requested.
 17. A Channel State Information(CSI) feedback method of a terminal, comprising the steps of: receivingan Uplink (UL) grant from a base station; analyzing a CSI request fieldof the UL grant; when the CSI request field is set to a request value,selecting a Downlink Component Carrier (DL CC) according to a ruleconfigured by a higher layer and DL CC identification informationincluded in the UL grant; generating CSI by measuring a channel state ofthe selected DL CC; and transmitting the CSI to the base station on theUL Component Carrier (UL CC) scheduled by means of the UL grant.
 18. TheCSI feedback method of claim 17, wherein selecting the DL CC comprisesselecting the DL CC indicated by a Carrier Indicator Field (CIF) of theUL grant according to the rule configured by the higher layer.
 19. Aterminal for feeding back Channel State Information (CSI) to a basestation, comprising: a receiver that receives an Uplink (UL) grant fromthe base station; a Physical Downlink Control Channel (PDCCH) decoderthat decodes a Channel State Information (CSI) request field of the ULgrant; an aperiodic CSI encoder that, when the CSI request field is setto a request value, selects a Downlink Component Carrier (DL CC)according to a rule configured by a higher layer and DL CCidentification information included in the UL grant, measures a channelstate of the selected DL CC, and generates CSI with the measured channelstate; and a transmitter that transmits the CSI to the base station onthe UL CC scheduled by means of the UL grant.
 20. The terminal of claim19, wherein the aperiodic CSI encoder selects the DL CC indicated by aCarrier Indicator Field (CIF) of the UL grant according to the ruleconfigured by the higher layer.